Studies On Facade Flame Behavior Ejected From Opening Of A Building Compartment Under Different External Boundary And Pressure Conditions

Flame ejecting behavior from a building facade opening (e.g., window, broken glass curtain wall), is a special phenomenon, with smoke, and sustained combustion outside the enclosure, it happens a lot in multi-storey and high-rise building fires. And exterior wall thermal insulation materials has been widely used in recent years, it is easy to form three-dimensional fire spread upward, cause a number of (many) layer burning at the same time, smoke and hot gases do harm to people’s life, and cause injury serious consequences. In real environment, building facade ejecting fire behavior characteristics will be subjected to the influence of different external boundary and pressure. For instance,(1) In some cities of China, there are many densely populated buildings (e.g., dense urban village buildings), due to the narrow floor spacing, when a building fire, overflow of flame through the building facade openings to the adjacent buildings and super structure caused great danger.(2) In some cities in China, due to the effect of natural terrain, lots of buildings were built on hillsides. For example, lot of tall buildings in Chongqing city were built on hillsides. As an impact of the hillsides, building facade flame ejecting behavior, flame and plume entrainment is different from normal buildings. However, very few researches on it have been done so far.(3) In plateau area, plateau with low pressure and relatively low oxygen concentration can make many different effects on flame ejecting behavior from a building facade opening. Therefore, we need to study the building facade ejecting behavior characteristics under different external boundary and pressure conditions.Experimental research, theoretical analysis, numerical simulation method were carried out to investigate the building facade ejecting fire behavior characteristics under different external boundary and pressure conditions. In order to carry out related research, a1:4and1:8scale model were established for fire simulation test device, respectively in Hefei and Lhasa plateau. Experimental measurement carried out to obtain parameters (flame height, radial and vertical temperature of ejecting fire plume, etc.) of flame ejecting behavior from a building facade opening, combined with knowledge of fire dynamics, evolution mechanism of building facade ejecting flame behavior characteristics were revealed under different external boundary and pressure conditions, and the corresponding dimensionless characteristic parameter theoretical prediction model was established. Specific work includes:Facade flame behavior and plume characteristics ejected from opening of a building compartment was carried out to study flame height and vertical temperature distribution under free boundary conditions, Based on the1/4scale building external facade flame test model, internal temperature rise of combustion chamber was analyzed through quantitative calculation of energy conservation, the relationship between internal temperature rise of combustion chamber and opening factor was revealed; And virtual point source concept in building facade fire was introduced firstly, coupling relationship model of highest temperature with opening size, HRR and characteristic length were established for building facade ejecting fire under the free boundary condition.Radial plume temperature profile of building facade ejecting fire under free boundary condition was revealed, based on the gaussian distribution function, theoretical model analysis was carried out to study radial plume temperature of the building facade ejecting fire and the1/4scale building facade fire model test, was used for validation, the results show that the proposed characteristic length scales of the effective plume thickness under different HRR can be very good correlation with different opening size. At the same time, radial plume temperature model of building facade ejecting fire behavior can well predict measured radial plume temperature of building facade ejecting fire.The differences of building facade ejecting fire behavior characteristics under vertical facing wall and sloping facing wall restrict was revealed. Through the experiment, validation analysis of building facade spacing between two vertical facing walls for ejecting flame height, it found the flame height and the dimensionless characteristic distance have better coupling relationship, shows the characteristics of two segmented function. And analyzed the impact of the angle of sloping facing wall on building facade ejecting fire behavior, the coupling relationship of the angle of sloping facing wall and the flame height are obtained. From the perspective of entrainment limit, the thesis analyses the differences between vertical facing wall and sloping facing wall restrict and have been characterized.Research reveals the difference of facade flame behavior and plume characteristics ejected from opening of a building compartment between the plain atmospheric region and plateau region. A1:8scale model of building facade ejecting fire test device was set up in Lhasa, building facade ejecting fire behavior characteristics was the quantitative analyzed in Hefei and Lhasa data (flame height, ejecting the plume parameters such as the vertical and the radial temperature distribution difference), and theory analysis was carried out to study external vertical temperature dacay characteristic, by the comparison with the experimental results, it concluded that entrainment intensity of building facade ejecting fire in Lhasa was about0.8times than that in Hefei. Flame height and ejected plume temperature model were fixed.